Gastric cancer (GC) can be considered an indicator of health disparity since it is more prevalent in developing countries, where the mortality is higher. In Mexico GC is the 3rd leading cause of mortality after CVD and lung cancer, and in the US, GC incidence is also higher in Hispanics than in white Americans. The etiologic factors for GC include Helicobacter Pylori infection, dietary factors and genetic susceptibility. Due to the large number of MA children residing in Texas, and the high prevalence of gastric disorders observed in our on-going study "Biomarkers of Genetic Susceptibility in Environmentally Exposed Migrant/Seasonal Farmworker Children (MSF Study), we propose to use a molecular and environmental epidemiologic approach to assess the prevalence of the aforementioned GC risk factors among this minority population. In addition, we will develop and validate a FFQ to assess the folate and vitamin B-12 intake of MA children residing in Texas. Our short-term goal is to estimate the magnitude of the prevalence of the social, environmental and genetic factors that have been associated with GC risk among MA children, with the long-term goal of reducing the risk that can be modified through preventive interventions. The specific aims of the study are to: 1. Generate epidemiological and dietary GC risk data from 500 MA children ages 5 to 18. We will obtain socioeconomic and dietary information, family history of GC and gastric disorders (GD), children's medical history and symptoms of GD via a structured bilingual questionnaire using indirect interviewing techniques with the mother and child participants. 2: Genotype a key gene involved in folate-DNA methylation as an intermediate biomarker for GC risk. We will genotype the children for polymorphisms in the methylenetetrahydrofolate reductase (MTHFR gene at position 677C>T since variability in this gene can critically influence the distribution and availability of folate, which in turn can increase the risk for GC. 3: Determine the folate, vitamin B-12 and homocysteine levels of the children. We will analyze the levels of folate in the erythrocytes and the homocysteine in the plasma of the children participants as intermediate biomarkers for GC risk since folate deficiency can lead to an accumulation of homocysteine, which in turn reduces the availability of methyl groups needed for DNA methylation 4. Determine the seroprevalence of antibodies against HP. We will analyze the serum of the children participants for the presence of IgG antibody against HP, which is an indicator of HP exposure, and a risk factor for GC. The ability to identify children are risk for GC, due to either genetic predisposition or environmental factors has substantial implication for cancer prevention. Findings from our study may also serve to reduce existent GC health disparities worldwide and in the U.S.